I purchased an Ameritron AL-811H amp. Per the tuning up instructions in the operator's manual on page 6, the plate current with no exciter drive should be 125 ma. My meter is indicating 175-180ma. Should I be concerned about this? I have the amp set for 240 volt operation. My line voltage reads about 241 volts. Other than this, the '811H still loads up per the operator manual.

Let's start again, for four tubes the max allowable dissipation is 260W at 1500V so with 125ma the tubes are within spec at 187.5W but with 175ma the total dissipation is 262.5W which puts the tubes slightly above their rated dissipation, so yes, I would say it is a bit high.

I have had a look at the manual and are you sure the tappings are correct? 241V should not make that much difference, if your line voltage is the same spec as ours it is plus or minus 10% of the nominal or declared voltage anyway.

I purchased an Ameritron AL-811H amp. Per the tuning up instructions in the operator's manual on page 6, the plate current with no exciter drive should be 125 ma. My meter is indicating 175-180ma. Should I be concerned about this? I have the amp set for 240 volt operation. My line voltage reads about 241 volts. Other than this, the '811H still loads up per the operator manual.

Thank you,Tom, N8EUI

What year was the amp made?

Tubes changed charateristics and started drawing more current. If it is an older amp without bias diodes, you might need to add about 3-4 volts of bias in the center tap lead. You can do that with a string of diodes.

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